Marked Improvement in H2S Scavenging, Oil Production, Separation, and Discharge Water Quality Experienced | Schlumberger
Case Study
Location
North Sea, Norway, Europe, Offshore
Details

A new environmentally acceptable H2S scavenger and corrosion inhibitor enabled higher production rates from high-H2S wells by removing more than 50% of the H2S before reaching topside facilities without modification of the chemical injection system. Overall improvement of the field’s environmental footprint also included reliable inhibition of CO2 corrosion in production tubulars, reduced H2S in the low-pressure parts of the process system to <1,000 ppm, reduced precipitation of iron sulfides, and improved water and oil separation.

Marked Improvement in H2S Scavenging, Oil Production, Separation, and Discharge Water Quality Experienced

Multifunctional H2S scavenger and corrosion inhibitor addresses integrity challenges and production output limitations of a mature subsea North Sea field

An Equinor subsea field with a prioritized KPI to reduce the environmental footprint produces to the installation via a carbon steel pipeline that was adversely affected by the corrosive production. The oil-producing wells are rich in H2S, and the existing triazine-based topside H2S scavenger injection system could not treat the gas phase, resulting in

  • H2S above export gas specifications
  • gas phases with 2,800 ppm of H2S in the low-pressure parts of the process system that represented increased health and safety risks at the degasser, as highlighted by field management as a major occupational risk requiring mitigation.

What they tried first

Current conditions were forcing Equinor to either shut down or choke high-H2S oil production while overinjecting triazine-based H2S scavenger topside, increasing the environmental footprint of production as well as the mineral scale precipitation potential.

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Multifunctional KI-3138 scavenger and inhibitor at 100 ppmv injection rate scavenged 470 kg of H₂S before production fluids reached the topside production manifold.
"Upon implementation of this product, the installation immediately saw improvement in separation and water quality. H2S level has been reduced to an acceptable level, and the installation is able to produce from wells with H2S restrictions. Implementation of KI-3138 has been a great success for Equinor."

Tore Rindalsholt, Production Chemistry, Equinor

What Schlumberger recommended

The Schlumberger Production Technologies KI-3138 H2S scavenger and corrosion inhibitor was used to scavenge H2S before it reached the topside production manifold to compensate for topside treatment limitations while protecting the integrity of the carbon steel subsea pipelines.

How the synergies boosted production

The introduction of multifunctional KI-3138 scavenger and inhibitor enabled higher production rates from the high-H2S contributing wells and reduced H2S in the low-pressure parts of the process system to <1,000 ppm while maintaining corrosion protection of the carbon steel subsea production pipeline. These results were achieved without modification of the chemical injection system or the topside process system, nullifying the need for capex.

Graph showing lower Fe minerals precipitation and materialization through improved water quality.
The KI-3138 scavenger and inhibitor injection plotted with iron concentration and suspended solids showed lower Fe minerals precipitation and materialization through improved water quality.
Graph showing lower Fe minerals precipitation and materialization through improved water quality.

As a supplementary effect, introduction of KI-3138 inhibitor improved water quality, making a positive impact on environmental impact factor (EIF) and environmental field footprint. Limiting available sulfide in the water phase reduced the precipitation of iron sulfide, which was previously shown to stabilize emulsions in the process train, thereby eliminating the water-capacity bottleneck at the second-stage separator.

View Technical Paper.

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